as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
Related Words
Relevance
Dissimilar Words
Example Sentences
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Recent Examples of insidious
What makes this deal particularly insidious is the trade-off at its core.
—
Joe Wilkins,
Futurism,
10 June 2026
But most of its failures are subtler, more insidious.
—
Katy Waldman,
New Yorker,
10 June 2026
But there is an insidious quality.
—
Rory McDonald,
Fortune,
6 June 2026
Best known for comedy series like Community (2009-15) and GLOW (2017-19), Alison Brie is taking on the role of Evil-Lyn, an insidious enchantress who serves as Skeletor’s main accomplice.
—
Keith Langston,
PEOPLE,
6 June 2026
See All Example Sentences for insidious
Joe Wilkins,
Futurism,
10 June 2026
But most of its failures are subtler, more insidious.
—
Katy Waldman,
New Yorker,
10 June 2026
But there is an insidious quality.
—
Rory McDonald,
Fortune,
6 June 2026
Best known for comedy series like Community (2009-15) and GLOW (2017-19), Alison Brie is taking on the role of Evil-Lyn, an insidious enchantress who serves as Skeletor’s main accomplice.
—
Keith Langston,
PEOPLE,
6 June 2026
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
-
The terrain can be treacherous, but the guide offered patience and grace for our entire group, slowing down without comment when someone was straggling and prioritizing water breaks.
-
Shinnecock’s fairways create optical illusions off the tee, the bunkering is treacherous and the greens are, in some places, designed to repel the ball from the putting surfaces.
Adjective
-
Available in a style with the same stripes that Paltrow favors, the top offers a subtle pattern that’ll make your outfit pop.
-
The square neckline adds a flattering, feminine touch, while the subtle volume in the sleeves gives it a slightly dressier feel than your average tee.
Adjective
-
According to the department, at the time of the chase, Buban had multiple outstanding arrest warrants against him, including for being a felon in possession of a firearm, taking a vehicle without consent, false impersonation and petty theft.
-
According to Peña, a producer relayed the false information to her through an earpiece during a live broadcast.
Adjective
-
Despite criticism over opaque and deceptive practices, prediction markets’ election favorites won most of the time, a Washington Post analysis found; more liquid in betting markets improves their accuracy, economists told CNN, but could carry negative social costs.
-
This is the essence of GPS spoofing, in which an attacker floods a GPS receiver with deceptive signals.
Adjective
-
This is perhaps the most perfidious practice of this sort of politics.
-
Pakistan was a perfidious ‘ally’ in Afghanistan, backing the Taliban while pretending to be our friends.
Adjective
-
Govern From Day One In a regulated context, an assistant that produces a confident but incorrect answer carries genuine regulatory and reputational exposure.
-
Many argue that signatures are invalid because signers listed incorrect addresses or live outside of the district the candidate wants to represent.
Adjective
-
Tom Kim dropped two shots at the wrong time and shot 72.
-
Every traveler has a trip that went spectacularly wrong.
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 26 Jun. 2026.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
